This study was designed to determine the rate of glucose production by the liver in patients with absent glucose 6 phosphatase, deficient glucose 6 phosphatase and deficient translocase I as well as type III glycogenosis. There are reports that the liver of patients with type I glycogenosis produce some glucose. This interpretation was to be tested to determine whether there is a detectable difference in glucose production by the liver of those individuals who have a total absence of glucose 6 phosphate in contrast with those with a partial defect. Similarly, is there a difference in patients with translocase I defect compared with glucose 6 phosphate defect? Is there a difference in liver glucose production by patients with the translocase I defect who have milder manifestations when compared with the more severely affected?